Magnetorheological fan coupling

ABSTRACT

A magnetorheological fan coupling ( 10 ) having a fan-drive subassembly ( 12 ), an electromagnet subassembly ( 14 ), and a magnetic medium ( 16 ). The fan-drive subassembly ( 12 ) includes an output member ( 22 ) and an input member ( 20 ) rotatably mounted around the output member ( 22 ) with the magnetic medium ( 16 ) therebetween. The magnetic medium ( 16 ) has a shear stress that can be adjusted by a magnetic flux ( 24 ) for transferring torque between the input member ( 20 ) and the output member ( 22 ). The electromagnet subassembly ( 14 ) includes a stationary electromagnet coil ( 62 ) for adjusting the shear stress of the magnetic medium ( 16 ) and regulating a torque transferred between the input member ( 20 ) and the output member ( 22 ).

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No. 11/163,629, which was filed on Oct. 25, 2005, entitled a “MAGNETORHEOLOGICAL FAN COUPLING,” and a continuation-in-part of U.S. patent application Ser. No. 10/908,965, which was filed on Jun. 2, 2005, entitled a “MAGNETORHEOLOGICAL FAN COUPLING,” and is related to U.S. patent application Ser. No. 10/929,801, which was filed on Aug. 30, 2004 and entitled an “ELECTRONICALLY CONTROLLED FLUID COUPLING DEVICE,” the disclosures of which are all incorporated herein by reference.

TECHNICAL FIELD

The invention generally relates to engine cooling systems for vehicles and more specifically relates to a magnetorheological fan coupling for an engine cooling system.

BACKGROUND ART

Viscous-fluid fan couplings for engine cooling systems play a significant role in conserving engine power and also enhancing overall vehicle performance.

Electrically actuated viscous-fluid fan couplings (i.e., electrical fan couplings) have a somewhat high number of parts for providing a precisely controlled output. Specifically, the typical electrical fan coupling includes a viscous fluid, a working chamber, a reservoir chamber, a series of valve mechanisms, and a computer that actuates the valve mechanisms for metering the flow of viscous fluid between the working chamber and the reservoir chamber. In this way, the computer can control the amount of fluid in the working chamber and selectively engage the coupling to provide a predetermined amount of output.

It would therefore be desirable to provide an improved fan coupling, particularly one having a robust construction composed of generally few parts.

SUMMARY OF THE INVENTION

One advantage of the invention is that a magnetorheological fan coupling (i.e., an MR coupling) is provided that has a stable and robust construction for thereby increasing the life of the MR coupling.

Another advantage of the invention is that an MR coupling is provided that has a relatively simple and compact construction with generally few components for thereby decreasing its manufacturing cycle time, as well as the cost associated therewith.

Yet another advantage of the invention is that an MR coupling is provided that effectively enhances the rejection of heat therein.

Still another advantage of the invention is that an MR coupling is provided that can be packaged within various-sized applications for use in a variety of different systems.

Yet another advantage of the invention is that an MR coupling is provided that utilizes a relatively low amount of power for moving between engaged and disengaged modes.

The above and other advantages of the invention are met by one or more embodiments of the present invention, which is an improvement over known viscous-fluid fan couplings.

The present invention enables an MR coupling having a fan-drive subassembly, an electromagnet subassembly, and a magnetic medium. The fan-drive subassembly includes an output member and an input member rotatably mounted around the output member with the magnetic medium therebetween. The magnetic medium has a shear stress that can be adjusted by a magnetic flux for transferring torque between the input member and the output member. The electromagnet subassembly includes a stationary electromagnet coil for adjusting the shear stress of the magnetic medium and regulating the amount of torque transferred between the input member and the output member.

Other advantages and features of the present invention will become apparent from the following description of the invention, when viewed in accordance with the attached drawing figures and also the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is described hereinbelow, by way of example, with reference to the following drawing figures.

FIG. 1 is a partially exploded perspective view of a magnetorheological fan coupling (MR coupling), therein illustrating the major subassemblies of the coupling, according to one embodiment of the present invention.

FIG. 2 is a perspective cross-sectional view of the MR coupling shown in FIG. 1.

FIG. 3 is a perspective cross-sectional view of the MR coupling shown in FIG. 1, according to another advantageous embodiment of the claimed invention.

FIG. 4 is a fully exploded perspective view of the MR coupling shown in FIG. 2.

BEST MODE(S) FOR CARRYING OUT THE INVENTION

Although the present invention may be used advantageously in coupling devices that have various configurations and applications, it is especially advantageous for driving a radiator cooling fan for an internal combustion engine (ICE). The present invention also is advantageous for concurrently transferring power to a waterpump subassembly, namely a series of impeller blades therein for pumping water through an engine block. Accordingly, the invention will be described below in connection therewith. However, it is to be appreciated that the invention can also be integrated with various other systems for other suitable applications as desired.

Referring to FIG. 1, there is shown a partially exploded view of a magnetorheological fan coupling 10 (i.e., an MR coupling), according to one advantageous embodiment of the claimed invention. The MR coupling 10 generally comprises a fan-drive subassembly 12, an electromagnet subassembly 14 (best shown in FIG. 2), and a magnetic medium 16. The electromagnet subassembly 14 magnetizes the magnetic medium 16 and actuates the fan-drive subassembly 12 in an engaged mode, a disengaged mode, and a range of partially engaged modes. In this embodiment, as detailed below, the MR coupling 10 further includes the waterpump subassembly 18 for rotating impeller blades therein and pumping water through the engine block.

As detailed below and shown in FIG. 2, the fan-drive subassembly 12 has an inverted construction comprising an input member 20 rotatably mounted around an output member 22. The output member 22 is selectively engaged with the input member 20 by the magnetic medium 16, which has a shear stress that can be regulated by the induction of various magnetic fields. The magnetic medium 16 preferably is a magnetorheological fluid (an MR fluid). However, the magnetic medium 16 can instead be a magnetic powder or other suitable equivalents thereof as desired. In the embodiments described below, the MR coupling 10 has an efficient construction that is configured for directing a magnetic flux 24 through the magnetic medium 16 so as to engage the coupling 10, minimize its power requirements, and decrease its overall size.

The input member 20 includes a pulley 26, a front-end structure 28, a hub 30, and a first threaded adapter 32. In this embodiment, the first threaded adapter 32 is fastened to a second threaded adapter 34, which is press fit or otherwise mounted to a pump shaft 36 of the waterpump subassembly 18. It is to be appreciated that the input member 20 can also have various other suitable constructions so long as the purposes of the invention are fulfilled.

The pulley 26 is driven by an engine crankshaft (not shown) via a belt 38. This pulley 26 is releasably attached to the hub 30 for easily removing the pulley 26 from the MR coupling 10. To that end, a larger or smaller sized pulley can be installed in the MR coupling 10 for use in various packaging applications such as, for example, in a variety of different sized vehicles. In this embodiment, the pulley 26 is releasably attached to the hub 30 by one or more threaded bolts 40. However, it is contemplated that other releasable fastening means can attach the pulley 26 to the hub 30 or other suitable coupling structure as desired. In an alternative embodiment, the pulley 26 can be fixedly attached to the MR coupling 10 by, for example, a press fit.

The front-end structure 28 is attached to and rotated by the pulley 26. In particular, the front-end structure 28 includes a body 42 and a cover 44 roll formed thereto. The body 42 is releasably attached to the hub 30 and the pulley 26 by the threaded bolt 40 and therefore rotates at the same rate as the pulley 26.

Furthermore, the cover 44 has a series of fins 46 for producing a cooling flow of air and rejecting heat in the MR coupling 10. In this respect, the inverted construction of the MR coupling 10 includes the fins 46 extending from the input member 20 rather than the output member 22. Accordingly, the front-end structure 28 cools the MR coupling 10 so long as the pulley 26 is being driven by the engine, thereby enhancing the rejection of heat. It is to be understood that the fins 46 can extend from other suitable portions of the MR coupling 10. For instance, as shown in FIG. 3, it is contemplated that both the body 42 and the cover 44 can have fins 46 as desired. The fins 46 are die cast, press fit, or otherwise suitably formed on the front-end structure 28.

The body 42 and the cover 44 define one continuous working chamber 48 with the magnetic medium 16 therein and the output member 22 rotatable therein. As detailed below, it is to be appreciated that the magnetic medium 16 effectively dispenses with the need for a reservoir chamber, valve mechanisms, and other known components of various fan drives.

As shown in FIG. 2, the working chamber 48 has a single-gap construction. In particular, the output member 22 includes an output shaft 50 and a rotor 52 extending orthogonally therefrom. The output shaft 50 is rotatably mounted to the cover 44 by a ball bearing 54 or other suitable attachment. The rotor 52 has an annular land 56 a with one output torque surface 58 a adjacent to one input torque surface 58 b on the body 42. These opposing surfaces 58 a and 58 b define a single gap in the chamber 48, which contains the portion of the magnetic medium 16 that transfers a substantial amount of the torque between the input member 20 and the output member 22. This operation is detailed below in the description for the electromagnet subassembly 14. As also detailed below and shown in FIG. 3, the working chamber 48 can have a multiple-gap (or multi-gap) construction with the input member 20 and the output member 22 having a series of opposing lands 56 a and 56 b with opposing torque surfaces 58 a and 58 b.

In this embodiment, the MR coupling 10 includes one or more seals 66 for sealing the magnetic medium 16 in the working chamber 48. For instance, the body 42 and the cover 44 have a seal 66 sandwiched therebetween, and the hub 30 and the body 42 also have a seal 66 sandwiched therebetween. The MR coupling 10 can also have various other seals 66 in other locations as desired.

Referring to FIG. 2, the MR coupling 10 further includes the electromagnet subassembly 14 for regulating the shear stress of the magnetic medium 16 and transferring torque from the input member 20 to the output member 22. The shear stress of the magnetic medium 16 disposes or sets the MR coupling 10 in an engaged state, a range of partially engaged states, or a disengaged state. In the engaged state, the magnetic medium 16 has a sufficiently high shear stress for transferring a significant amount of torque between the input member 20 and the output member 22. In the disengaged state, the magnetic medium 16 has a sufficiently low shear stress for transferring little to no torque between the input member 20 and the output member 22. Thus, the shear stress of the magnetic medium 16 in the chamber 48, in conjunction with the rotational speed of the input member 20, determines the amount of torque actually transferred to the output member 22. Put another way, the torque response is a result of the shear stress existing within the working chamber 48.

To that end, the electromagnet subassembly 14 includes a stationary electromagnet coil 62 for producing a magnetic flux 24 directed between the torque surfaces 58 a and 58 b and through the magnetic medium 16. In particular, the fan-drive subassembly 12 has a series of ferrous structures and nonferrous structures configured to form a magnetic circuit 64 that directs the magnetic flux 24 through the magnetic medium 16.

With attention to FIG. 2, the ferrous structures include the first adapter 32, the second adapter 34, the output shaft 50, the rotor 52, the land 56 a, the body 42, and the pulley 26, which each comprise steel or some other suitable ferrous material(s). In addition, the coil 62 is fixedly mounted to the MR coupling 10 by a ferrous housing 68, which completes the magnetic circuit 64. In this embodiment, the ferrous housing 68 comprises steel and is press fit to a stationary waterpump housing 70.

The nonferrous structures extend between the ferrous structures so as to prevent a short-circuit condition in the magnetic circuit 64, which could otherwise decrease or eliminate the magnetic flux 24 through the magnetic medium 16. For example, in both the single-gap construction and the multiple-gap construction respectively shown in FIGS. 2 and 3, the hub 30 comprises aluminum or some other suitable nonferrous material so as to prevent a short-circuit condition between the first adapter 32 and the pulley 26. Moreover, with regard to the multiple-gap construction, the rotor 52 has one or more ferrous annular lands 56 a, which have the output torque surfaces 58 a thereon and a nonferrous extension member 72 therebetween. In this way, the magnetic flux 24 is directed through the magnetic medium 16 between each land 56 a and 56 b. It is to be understood that otherwise connecting the lands 56 a with a ferrous extension member would create a short-circuit condition between the rotor 52 and the outermost land 56 a. In the same regard, the cover 44 comprises nonferrous material and has one or more opposing ferrous annular lands 56 b, which have the opposing torque surfaces 58 b thereon. The nonferrous cover 44 is roll formed around the periphery of the ferrous body 42 for directing the flux 24 between the outermost land 56 a on the rotor 52 to the body 42. The lands 56 a and 56 b are die cast, press fitted, integrally formed, or otherwise attached to the rotor 52 and the cover 44 by other suitable means.

It is contemplated that the fan-drive subassembly 12 or other portions of the MR coupling 10 can have a variety of other suitable configurations including ferrous structures, nonferrous structures, or any combination thereof so long as the purposes of the claimed invention are generally accomplished.

The electromagnet subassembly 14 further includes a controller 74, one or more sensors 76, and a power source 78. The controller 74 receives signals from the sensors 76 for thereby detecting various vehicle conditions. The controller 74 processes these signals for determining an amount of electrical power to supply to the coil 62 and then actuates the power source 78 so as to provide the predetermined amount of power to the coil 62 by, for example, pulse-width modulation (PWM). In this way, the controller 74 precisely regulates the amount of magnetic flux 24 in the magnetic circuit 64 so as to control the shear stress of the magnetic medium 16 and hence control the output of the MR coupling 10.

In this embodiment, the controller 74 receives electrical signals from an output differential speed sensor 90 regarding the engagement between the input member 20 and the output member 22. For example, a zero speed differential sensed between the input member 20 and the output member 22 can indicate that the MR coupling 10 is in a fully engaged state. As shown in FIG. 2, the output speed differential sensor 90 is sandwiched between the output shaft 50 and the second adapter 34. However, it is to be understood that the sensor 90 can be installed within the MR coupling 10 in other suitable locations and by other means. Furthermore, other sensors 76 can be utilized for detecting engine temperature, fuel economy, emissions, or other engine operating conditions.

For instance, in another embodiment, the sensors 76 include a water temperature sensor (not shown) for the engine. The controller 74 has a reference table stored therein for determining a desired engine temperature for a given engine speed. When the controller 74 determines that the engine temperature or engine water temperature is above a predetermined high threshold, the controller 74 actuates the power source 78 to provide full or varying power to the coil 62 to produce a maximum-strength flux so as to increase the shear stress of the magnetic medium 16. Accordingly, the magnetic medium 16 provides a maximum torque response of the rotor 52 for rotating the output shaft 50 and the radiator cooling fan coupled thereto. In other words, the magnetic medium 16 has sufficiently high shear stress for placing the MR coupling 10 in a fully engaged state.

Conversely, if the controller 74 determines that the engine temperature or the engine water temperature is below a predetermined minimum threshold, the controller 74 then sends a signal to the power source 78 to activate the coil 62 to a desirable pulse width so as to decrease the power supply for the coil 62. In particular, the coil 62 produces a magnetic flux 24 for adjusting the shear stress of the magnetic medium 16 so as to transfer less torque from the input member 20 to the output member 22. In this way, the MR coupling 10 is set in a partially engaged state for rotating the output member 22 and the radiator cooling fan attached thereto at a slower rate, thereby allowing the temperature of the engine to increase.

In this embodiment, the electromagnet subassembly 14 is stationary for thereby minimizing wear on the electrical circuitry therein. Specifically, as introduced above, the waterpump subassembly 18 has a pump housing 70 with a series of through-holes 82 for receiving bolts, such as bolt 40, or other suitable fasteners and fixedly attaching the pump housing 70 directly to the engine block face (not shown) or other suitable vehicle fixture. The pump housing 70 has the electromagnet subassembly 14 and its electrical circuitry mounted therein by the steel housing 68. In this respect, the electrical portion of the MR coupling 10 is not physically attached to the moving drive components but rather is mounted to a stationary fixture. As such, there is no tethered wire harness and no actuator bearing. This stable and robust construction is beneficial for increasing the life of the MR coupling 10. In addition, the electromagnet coil 62 can be more easily replaced, and thus lower costs related to service and warranty are realized.

Furthermore, this construction includes a substantial portion of the actuator components as integral parts of the engine side of the MR coupling 10. This feature leads to a lower overhanging mass on the drive components, which then leads to a higher system resonant frequency and also possible improvements in waterpump durability. Furthermore, this construction has a compact packaging that increases the available space within an engine compartment.

It is to be further appreciated that the MR coupling 10 effectively eliminates a substantial number of pumping mechanisms that are typically integrated within conventional viscous couplings. Thus, the MR coupling 10 has an inherently stable construction that can be quickly manufactured at a low cost.

While the present invention has been described in connection with one or more embodiments, it is to be understood that the specific mechanisms and techniques that have been described herein are merely illustrative of the principles of the invention, and that numerous modifications may be made to the methods and/or apparatuses described herein without departing from the spirit and scope of the invention as defined by the appended claims. 

1. A magnetic coupling comprising: an electromagnet; a drivable input member rotatably mounted proximate said electromagnet; an output member rotatably mounted proximate said electromagnet such that said input member is rotatably mounted about said output member; and a magnetic medium having an associated shear stress and disposed within a substantially closed and continuous work chamber defined between said input member and said output member; wherein said electromagnet is activatable to generate a magnetic field and thereby adjust said shear stress of said magnetic medium so as to regulate the transfer of any torque from said input member and to said output member; and wherein said input member has a plurality of external fins for producing a flow of air that cools said magnetic coupling when said input member is driven to rotate.
 2. A magnetic coupling as set forth in claim 1, wherein said input member includes a pulley by which said input member is drivable by a belt.
 3. A magnetic coupling as set forth in claim 2, wherein said input member is structurally adapted so that said pulley is selectively removable therefrom and also installable thereon.
 4. A magnetic coupling as set forth in claim 1, wherein said input member is structurally adapted for having any one of a series of different-sized pulleys selectively installed thereon for use in one of a plurality of different-sized vehicles.
 5. A magnetic coupling as set forth in claim 1, wherein said output member is structurally adapted for having a fan coupled thereto.
 6. A magnetic coupling as set forth in claim 1, wherein said magnetic medium comprises a magnetorheological fluid.
 7. A magnetic coupling as set forth in claim 1, wherein said magnetic medium comprises a magnetic powder.
 8. A magnetic coupling as set forth in claim 1, said magnetic coupling further comprising a controller coupled to said electromagnet.
 9. A magnetic coupling as set forth in claim 8, said magnetic coupling further comprising a sensor that is coupled to said controller and operable to sense temperature.
 10. A magnetic coupling as set forth in claim 8, said magnetic coupling further comprising a sensor that is coupled to said controller and operable to sense any rotational-speed differential between said input member and said output member.
 11. A magnetic coupling for a fan, said magnetic coupling comprising: a controller; an activatable electromagnet coupled to said controller; a drivable input member rotatably mounted proximate said electromagnet; an output member rotatably mounted proximate said electromagnet such that said input member is rotatably mounted about said output member; and a magnetic medium having an associated shear stress and disposed within a substantially closed and continuous work chamber defined between said input member and said output member; wherein said controller is operable to activate said electromagnet so as to generate a magnetic field and thereby controllably adjust said shear stress of said magnetic medium for regulating the transfer of any torque from said input member and to said output member; wherein said input member has a plurality of external fins for producing a flow of air that cools said magnetic coupling when said input member is driven to rotate; and wherein said output member is structurally adapted for having said fan coupled thereto.
 12. A magnetic coupling as set forth in claim 11, wherein said input member includes a pulley by which said input member is drivable by a belt.
 13. A magnetic coupling as set forth in claim 11, wherein said magnetic medium comprises a magnetorheological fluid.
 14. A magnetic coupling as set forth in claim 11, wherein said magnetic medium comprises a magnetic powder.
 15. A magnetic coupling as set forth in claim 11, said magnetic coupling further comprising a sensor that is coupled to said controller and operable to sense any rotational-speed differential between said input member and said output member.
 16. A magnetic coupling for a fan, said magnetic coupling comprising: a controller; an activatable electromagnet coupled to said controller; a drivable input member rotatably mounted proximate said electromagnet; an output member rotatably mounted proximate said electromagnet such that said input member is rotatably mounted about said output member; and a magnetic medium having an associated field-sensitive viscosity and disposed within a substantially closed and continuous work chamber defined between said input member and said output member; wherein said controller is operable to activate said electromagnet so as to generate a magnetic field and thereby controllably adjust said viscosity of said magnetic medium for regulating the transfer of any torque from said input member and to said output member; wherein said input member has a plurality of external fins for producing a flow of air that cools said magnetic coupling when said input member is driven to rotate; and wherein said output member is structurally adapted for having said fan coupled thereto.
 17. A magnetic coupling as set forth in claim 16, wherein said input member includes a pulley by which said input member is drivable by a belt.
 18. A magnetic coupling as set forth in claim 16, wherein said magnetic medium comprises a magnetorheological fluid.
 19. A magnetic coupling as set forth in claim 16, wherein said magnetic medium comprises a magnetic powder.
 20. A magnetic coupling as set forth in claim 16, said magnetic coupling further comprising a sensor that is coupled to said controller and operable to sense any rotational-speed differential between said input member and said output member. 